With help from Greeks, tragedies and other tales

Here's a quote. "Extremism in the defense of liberty is no vice." So said Barry Goldwater, who never got to be president, but whose sentiments will always have plenty of supporters.

Here's another quote. "Evil stays evil until the end, and goodness good." So wrote the dramatist Euripides in the 5th Century B.C., and documentary filmmaker Jessica Yu ("In the Realms of the Unreal") answers that with a firm "not so fast there."

What she has made, exactly, is a little less firm. "Protagonist" offers four intertwined stories of personal extremism and redemption, spanning the globe, with excerpts from "The Bacchae" and other ancient Greek classics deployed as choral commentary performed by on-screen rod puppets. Already that's a lot more going on than a typical documentary.

Yu's subjects are a fascinating lot. Hans-Joachim Klein, a German radical, becomes a terrorist, then accomplice to kidnapping and murder. Mark Pierpont, a New Jersey native, suppresses his homosexuality and channels his energies into missionary work, only to find out that some things cannot be suppressed. Mark Salzman (Yu's husband) transforms himself from a bullied school kid into a martial arts obsessive, under the dubious guidance of a fascistic instructor.

The most compelling stories belong to Joe Loya, a friend of Yu's whose violently abusive childhood paves the way for a life of rage and crime, eventually leading to 30 bank robberies. "I didn't want to be the victim anymore," he says. "I wanted to be the victimizer." It is a harsh but universal impulse, and it is the opposite of enlightenment. In prison Loya learned how to devote himself to better things and to exorcising his demons.

All four stories are worthwhile, though together they're an awful lot for one modest doc to cover. Yu's integration of cinematic and theatrical elements is uneven, and a bit stiff. Still, many will be moved by "Protagonist" and its reminders that we are all struggling to find versions of ourselves to live up to.